1. Field of Invention
The present invention relates to an LED (light emitting diode) drive circuit, and more particularly to an LED constant-current drive circuit.
2. Description of Related Arts
LEDs are quickly applied to all areas for long service life, high luminous efficiency, low power consumption and no radiation characteristics in our daily life. However, the PN junction of the LEDs also has the same characteristic of that of the diode (nonlinearity) and has a negative temperature coefficient. Therefore, while using the LEDs, it is required for the driving power to have a high stability and a constant current characteristic. The resistance-capacitance driving circuit is a commonly used LED driving circuit. Under the high voltage, its current increases sharply, its power factor is lower and its higher harmonic is more. Currently, there are also some special LED constant-current drive chips with high stability and good constant-current characteristic on the market. However, these special LED constant-current drive chips have complicated structure, high cost and high price.